This invention relates generally to restricting access to selected controls in a signal receiver and is particularly directed to a secure system for restricting tuning access to a limited number of designated channels in a satellite television receiver.
An increasing number of channels are being made available to the television viewer. This increase in television channel viewing availability is due to increasing numbers of cable television (CATV) networks as well as to the increasing use of satellites to relay transmitted television signals back to the earth. Such satellites are typically provided with antenna arrays which offer large areas of coverage of the surface of the earth. These communications satellites, which are in stationary orbit far above the earth's surface, are typically capable of re-transmitting as many as 24 channels. With the number of communications satellites now in use exceeding 20 and more scheduled for use in the near future, it can easily be seen that a television viewer may have in excess of 100 additional channels available for viewing.
Not all of these channels may be suitable for viewing by all members of the family. Thus, many parents would like to be able to limit viewing of their children to only programs suitable for a given age group. Various arrangements are currently available for providing limited viewing access.
One approach for limiting viewing access in a satellite television receiver makes use of a remote control transmitter which selectively disables the television receiver for preventing tuning to certain designated channels. Only designated channels may be tuned to using a television receiver-mounted channel selector when the remote controller is removed. This approach takes away a main convenience feature, i.e., remote control, is awkward to control, and thus has limited commercial appeal.
Another common approach to limiting channel viewing access involves the use of a password which is generally in the form of a multi-digit code word which either disables or enables the satellite television receiver in limiting channel viewing access as desired. One problem with this approach relates to the difficulty of remembering a multi-digit code. In some addressable systems, if the coded password is forgotten, a central controller must be contacted typically by telephone to allow for the entry of another password after the previously entered coded channel accessing entries are erased by the central controller. In order to avoid difficulties encountered when a password is forgotten, one current approach limits the effective time of an entered password to 12 hours. Following this predetermined time period, restricted access to any of the television channels is removed and all channels may be viewed. While limiting the inconvenience of a forgotten password to a predetermined period, this approach nevertheless requires user recall of the password over an extended time interval and requires reentry of a password every time limited channel viewing access is desired.
Still other restrictive access control systems allow for the entry of a new password if the previous password is forgotten. This approach can, of course, lead to abuses as any viewer can enter the new password and gain access, or restrict access, to any channel.
The present invention represents an improvement over the aforementioned approaches to restrictive access control systems by providing a key actuated 3-position control switch which affords three modes of operation for a satellite television receiver. One mode of operation permits all channels to be viewed, a second mode of operation permits selected channel access information to be stored in memory for subsequent recall, while a third mode of operation permits tuning to only those channels having authorized access information previously stored in memory. In the first and third modes of operation, the key can be removed from the 3-position switch to either permit all channels to be viewed or to provide only limited access to a predetermined number of channels. The present invention permits various satellites to be selectively accessed and precludes unauthorized satellite access by allowing for only authorized receiver antenna positioning control while also providing for only authorized channel viewing of selected channels of an authorized satellite.
While the invention will be explained hereinafter in terms of a restrictive access television viewing system, it is also applicable for restricting access to receiver functional controls other than channel selection, and especially to those controls subject to accidental misadjustment. For example, the restrictive access system of the invention may be applied to such receiver control functions as polarization angle of the received signal, polarity switching, tuning of audio subcarriers, etc.